The present invention is related to a novel method for improving the quality of the steam produced by boilers through the removal of water therefrom while economically preheating the feedwater supplied to such boilers. Steam quality is the percentage of feedwater vaporized to steam. In once through type boilers 70 to 90% of the feedwater is converted to steam. The unvaporized water contains and carries dissolved solids and scale forming minerals. When the feedwater contains very high quantities of dissolved solids, silica and other solid impurities, the boilers must operate at lower levels of steam quality. The method of the present invention increases steam quality by first separating the unvaporized water containing the solid impurities and thereafter recovering part of such water and its heat content. The method is particularly applicable to commercial boilers producing saturated to moderately superheated steam at pressures of as great as 2900 psig. Typical of the commercial boilers to which the present thermodynamic method may be applied are oil field steamers, steam generators, hot water floods (fired by crude oil, refined oil or gas), or fluidized or circulating bed combustors burning coal, peat, wood wastes, municipal and household wastes, and waste sludges.